There are two options:
1) update the firmware on the BV500 (*recommended)
2) use BVserial version 15 or less, version 15 is still on the website (http://www.byvac.com/index.php/Downloads)

I would however update the firmware to 2.32 (http://www.bypic.co.uk/index.php/ByPic_Firmware). Just make sure that the DTR line is connect, i.e. when you press .r on BVserial it resets the BV500, this connection is normally optional but the boot loader requires it.